1. Field of the Invention
The invention lies in the field of automotive technology. More specifically, the invention pertains to voice command acquisition and speech recognition in motor vehicles.
Vehicle speech recognition systems require capturing the user voice input, which is then analyzed and reduced into a specific grammar used to input information into infotainment or integrated vehicle systems.
In many cases, the vehicle environment is too noisy to properly capture the user audio input (e.g. open sun roof, open windows, ventilation fan at high setting, or the like). The quality and accuracy of speech recognition algorithms are directly affected by the amount of noise present in the audio signal, in relation to the vocal audio information.
2. Description of the Related Art
German published patent application DE 43 25 404 A1 discloses a speech recognition system in which noise signals and background noise signals are eliminated so as to achieve better recognition. A catalogue of background noises are thereby stored in code books. Upon the input of a corresponding signal, the code books are queried and the background noise is eliminated, in case it is a known noise. If a given noise source is recognized by the system, it is also possible to issue a command signal to temporarily eliminate the noise source, for example, by automatically turning down the blower fan, or by closing a window.
A variety of additional efforts have been made in the prior art so as to improve speech recognition by eliminating noise signal components. For example, Japanese patent application JP 10 009 016 A reduces the speed of the blower fan of it's A/C unit when speech has been recognized in connection with a radio communication unit. German published patent application DE 41 06 405 A1 describes a speech recognition system in which background noise is analyzed and compensated. Further, the system determines if, and by how much, a window is open and the speech recognition processing is adapted accordingly. U.S. Pat. No. 7,171,365 B2 determines a background noise so that the same may be compensated during the speech recognition.
All of these approaches have in common that the noise signal is acquired and analyzed electronically within the speech recognition system. The focus for solving the technical issues concerning noise disruption lies on advances in microphone technology, improving processing algorithms for noisy signals, or the elimination of speech as a feature for models with a high assumed noise level (e.g., a convertible).
In certain vehicle speech recognition systems the audio speakers may be muted when a push-to-talk button is activated. In the alternative, as described in Japanese patent application JP 59 102 633 A, the driver may issue a voice command “be quiet.” In response, the speaker volume may be reduced, the blower fan may be turned down, and windows or the sunroof may be closed.